<select name="gru_id" <?php echo $estilo; ?>>
    
    <option value=""><?=$t_grupo_atuacao;?></option>

    <?php
    $sql_gru_id = "SELECT * FROM grupo WHERE status='1' ORDER BY gru_nome";
    $res_gru_id = sql($sql_gru_id);
    while($linha_gru_id = mysql_fetch_array($res_gru_id)){
    ?>

    <option value="<?=$linha_gru_id['gru_id'];?>" <?php if($linha_gru_id['gru_id'] == $gru_id) { echo "selected"; } ?>><?=$linha_gru_id['gru_nome'];?></option>

    <?php } ?>

</select>